Ignition arrangement for internal combustion engines



IGNITION ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES 2 Sheets-Sheet 1 Filed May 6, 1966 July 16,1968 G. SOEHNEH! ET AL 3,392,717

IGNITION ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES Filed May 6, 1966 2 Sheets-Sheet 2 W m -m Mum/r04 w $64M- W 14 401 United States Patent 11 Claims. Cl. 123-148 ABSTRACT OF THE DISCLOSURE An arrangement for igniting a plurality of spark plugs in an internal combustion engine, at the same instant of time. Each spark plug is provided with a separate ignition coil having primary and secondary windings. The secondary winding is connected to the spark plug for providing a high voltage pulse to the latter. The primary winding is controlled and operated by a transistor which is connected in series with a control path. Each primary winding of each ignition coil is provided with a separate one such transistor. A single power supply furnishes the electrical energy required for igniting all of the spark plugs. A switching arrangement operated as a function of the speed of the engine actuates a control path and thereby provides the pulse signal to the primary winding of the ignition coil for igniting the respective spark plug. The arrangement is such that ignition of at least one of the spark plugs is assuredupon failure of one of the operating elements in the control circuitry.

The present invention relates to ignition arrangements for igniting simultaneously and at the same instant of time, two spark plugs associated with an internal combustion engine.

Experience has shown that definite benefits may be derived through the use of two spark plugs in connection with the ignition of the air-fuel mixture within a cylinder of an internal combustion engine. By firing the two spark plugs at the very same instant of time, the effectiveness of ignition is increased, and thus the combustion of the mixture within the cylinder is more complete and more uniform. He-retofore, the firing of such two spark plugs was accomplished by means of two mechanically operated switches coupled to the internal combustion engine and actuated thereby, Mechanically operated switches of this type present synchronization problems since it is ditficult to install and adjust them so that they open and close the respective circuits at the same instant of time. Furthermore, such switches are also unstable with respect to maintaining such adjustments over any extended period of time. Thus, even though they may be adjusted intially in the proper manner, they cannot be expected to retain this adjustment after they have been actuated an exended number of times. Aside from this, such mechanically operated switches require considerable space for their installation.

It is therefore an object of the present invention to provide an ignition arrangement capable of generating signals in the form of pulses for firing two spark plugs at the very same instant of time.

It is another object of the present invention to provide ignition means of the type set forth which is fully reliable in its operation.

A further object of the present invention is to provide ignition means of the type set forth which is structurally simple, contains a minimum number of elements, and is compact.

With the above objects in view, the invention mainly consists in an ignition arrangement for internal combustion engines comprising, in combination, ignition coils having primary and secondary windings inductively linked, transistor circuits for driving the primary windings of said ignition coils, and a switching means which generates a pulse that is transferred to the transistor circuits and induces a corresponding high-voltage pulse suitable for firing the spark plug, in the secondary windings of the ignition coils.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a schematic circuit diagram of one embodiment of the invention, and shows transistors associated with the ignition coils as well as the switching means which generates the signals for controlling the state of the transistors; and

FIG. 2 is a schematic circuit diagram of another embodiment of the invention including a pulse emitter and a monostable Inultivibrator within the signal generating circuit.

In spark plug ignition circuits, the primary winding of the ignition or induction coil, normally carries a current which is interrupted at the desired moment for firing the spark plug connected to the secondary winding of the ignition coil. The resulting change in current flow in the primary winding, alters the magnetic field linking the primary and secondary windings, and causes a highvoltage pulse :to be induced in the secondary. The induced high-voltage pulse fires its cor-responding spark plug by jumping across the gap of the spark plug electrodes.

Referring to the drawings, and particularly to FIG. 1, the combustion engine is indicated by the block marked B. The engine includes a combustion cylinder having two spark plugs 1 and 2 associated with it. These spark plugs are electrically connected to one terminal of the secondary windings 3 and 4 of ignition coils 5 and 6, respectively. Each one of the other terminals of the sec ondary windings 3 and 4 of the coils 5 and 6, respectively, are connected to tthe negative pole of a direct-current power supply 9. One of the terminals of the primary windings 7 and 8 of the ignition coils 5 and 6, are also connected to the negative potential of the power supply.

The circuits of the primary windings 7 and 8 are coupled to two transistors T and T respectively. These transistors are normally in the conducting state. A switching means is provided for the purpose of cutting off these transistors at the ignition instant. This switching means 10 is associated with the engine B by being a mechanically driven cam which serves as a circuit breaker. The cam of the switching means 10 is mechanically coupled to the drive of the engine B.

Both transistors T and T are of the p-n-p type. Their collectors 11 and 12 are connected to the primary windings of the ignition coils 7 and 8 respectively. The emitters 13 and 14 of the transistors are connected to the positive terminal of the power supply 9, by means of switch 24. The transistor base 15 is coupled to its emitter 13 through means of resistor 17, and it is also coupled by means of resistor 19, to the switching means 10 which is in series with the negative pole of the power supply 9 when the switching means is closed. In a similar manner, the base 16 of transistor T is connected to its emitter 14 by way of resistor 18, and it is also connected to the switching means 10 through means of resistor 20. Ac-

cordingly, resistors 19 and 26 are commonly joined at the switching means 10. This junction point is maintained at the negative potential of the power supply, provided that the switching means 10 is closed. The resistors 19 and 20 may be functionally replaced by a common rcsistor 21 (indicated by dotted lines in FIG. 1), but with this design, it is essential to include the two diodes 22 and 23 in series with the bases 15 and 16 respectively.

The switch 24 serves as the main control element of the circuit. By being connected in series with the power supply 9, it can either energize or tie-energize the entire circuit through its closed or open positions. The circuit is completed by the capacitor 25 which is connected in parallel with the series combination of the power supply and'the main control switch 24.

The embodiment of the circuit as shown in FIGURE 1, operates as follows:

When the internal combustion engine B causes the switching means mechanically coupled thereto to open, the bases 15 and 16 of transistors T and T become disconnected from the negative potential of the power supply 9. The potentials of the bases 15 and 16 thus become positive as a result of being connected to the resistors 17 and 18 which are, in turn, coupled to the positive pole of the power supply. In this state, therefore, the emitter-collector circuits of transistors T and T are cut off or non-conducting. The change in the transistor state from conducting to non-conducting causes a step input to be applied to the primary windings 7 and 8 of the ignition coils and 6. This step input causes a corresponding step output to be induced in the secondary winding of the ignition coil. Due to the relative num ber of turns of the primary and secondary windings, the output voltage level of the secondary windings is magnified in relation to the input level at the primary windings. For example, the ignition coils are, in principle, .induction coils with primary and secondary windings magnetically coupled to one another. The secondary winding has many more turns than the primary winding for the purpose of raising the level of any voltage appearing at the primary. In this respect, the ignition or induction coil operates similar to the electrical transformer. The magnification of the input level at the primary is essential, because the induced level at the output of the secondary winding is routed to the spark plug which requires a high potential to fire or jump its air gap. Thus the spark plug, as used in practice, includes two electrodes separated by an air gap. The spark plug is operated or fired by causing a single voltage to jump the air gap between the electrodes. Once the spark plug is fired, the combustible fuel-air mixture in the engine cylinder becomes ignited.

The transistors T and T are coupled to the switching means 10 so as to assure that the two spark plugs 1 and 2 are fired at the very same instant of time. The resistors 19 and 20 serve to apply the potentials to bases and 16 respectively which are required to cause the emitteracollector circuits of transistors T and T to conduct. At the same time, the resistors 19 and 20 serve to properly de-couple the transistors from one another. In the event that a common resistor 21 is applied to replace the two resistors 19 and 20, the de-coupling function can be carried out by the two diodes 22 and 23. The capacitor 25 connected across the power supply when the main control switch 24 is closed, serves to depress stray signals and noise which may be generated by the firing of the spark plugs or the switching operations of the circuit.

The embodiment of FIGURE 2 differs from that of FIGURE 1 in that an electronic circuit is employed for the purpose of switching the states of the transistors T and T and hence the primary windings of the ignition coils 5 and 6. In this embodiment the common resistor 21 and the diodes 22 and 23 are utilized. The

electronic switching circuit consists of a monostable multivibrator circuit 29 which is coupled to the ignition coil circuits through means of the transistor T The later is of the p-n-p type, and its emitter 26 is connected jointly to the diodes 22 and 23. The circuit to the right of these diodes in FIGURE 2, is identical to the corresponding circuit in FIGURE 1. Thus, the diodes 22 and 23 are, in turn, connected to the bases 15 and 16 of transistors T and T respectively. The collector 27 of the transistor T is connected to the common base resistor 21 of the transistors T and T which is, in turn, connected to the negative pole of the power supply 9. The base 28 of the driving transistors T is connected to the output of the monostable multivibrator 29 which is outlined by dash-dot lines.

The multivibrator circuit 29 includes two transistors T and T which are both of the p-n-p type. In the normal state, transistors T and T are conducting, and transistor T is cut off. The emitter 30 of transistor T is connected to the positive pole of the power supply 9, whereas the collector 31 is directly connected to the base 28 of the driving transistor T The collector 31 is also connected to the negative pole of the power supply through means of the resistor 32. The base 33 of the transistor T is connected to the junction of resistors 34 and 35 which serve as a voltage divider. The junction of the base 33 and the voltage divider is, in turn, connected to one terminal of a coil 36 which is magnetically linked to the operating means of the engine B. The other terminal of coil 36 is connected to the positive pole of the power supply.

The coil 36 is a pulse emitter which becomes actuated when its magnetic field is altered. For example, in the normal state the coil 36 has a magnetizable core about which magnetic lines of force prevail clue to the current through the coil. The generator G associated with the coil, is a cam which has a magnetizable projection at its surface. The cam is mechanically driven by the engine B, and is situated with respect to the core of coil 36 so that the projection of the cam may pass closely by the core as the cam is rotated. When the cam projection made of magnetic material, thus passes by the core of coil 36, the magnetic field of the core is disturbed, and as a result a pulse is induced within the coil 36. It is not necessary that the magnetizable projection be attached to a cam. Any suitable mechanical moving means may be utilized to convey the magnetic material past the core of coil 36. The cam design has been described for illustrative purposes only.

A Zener diode 37 is connected in parallel with the coil 36 to limit the magnitude of the pulse that may be induced within the coil. The diode 37 thus acts as a safety means which protects the electronic circuitry actuated by the induced pulse of coil 36. The resistor 34 is connected to the positive pole of the power supply, while the resistor 35 is connected to the collector 38 of the conducting transistor T Aside from this, the collector 38 of transistor T is connected to the negative pole of the power supply 9 through means of the resistor 39. The emitter 40, on the other hand, is connected to the positive pole of the power supply. The base 41 is connected to the negative pole of the power supply through means of resistor 42, and it is also coupled by way of capacitor 43, to the collector 31 of the cut-off transistor T All remaining reference numerals in FIGURE 2 which have not been mentioned in the description of the embodiment of that figure, correspond identically to the reference numerals described in relation to the elements of FIGURE 1, and their function will, therefore, not be repeated.

The operation of the circuit of FIGURE 2 differs from that of FIGURE 1 in the following manner:

The pulse induced in coil 36 through means of the generator G, is limited by the diode 37 and applied, through means of the voltage divider 34-35, to the base 33 of transistor T This causes the base 33 to become negative and the transistor T to conduct. As a result the emitter-collector circuit with series resistor 32, applies a positive potential to the base 28 of the transistor T and causes the latter to be, thereby, cut olf. The cut-01f or non-conducting state of transistor T is analogous to the opening of switching means described in relation to FIGURE 1. Accordingly, the operation of the ignition coils 5 and 6 is similar to that described for FIGURE 1, when taken from this point.

During this switching transition of the circuit, the transistor T is also cut oil. The transistor T is maintained in this latter cut-off state until the capacitor 43 bridging base 41 and collector 31, has become discharged through the resistor 42. The non-conducting state of transistor T maintains the base 33 of transistor T at a negative potential as a result of the coupling of collector 38 with the base 33 through means of resistor 35. Accordingly, transistor T is stably held in the conducting state as long as transistor T is cut ofi. However, after the capacitor 43 has become discharged, the potentials of collector 38 and base 33 return to their normal state, and as a result the monostable multivibrator circuit 29 is returned to its initial position.

It is also possible to control the transistor T by means of the switching arrangement 10 shown in conjunction with the embodiment of FIGURE 1. In such a case (illustrated in phantom in FIGURE 2) the base 28 acquires a negative potential through resistor 44 when the switching means 10 is closed. When, on the other hand, the latter opens for purposes of igniting the spark plugs, the base assumes a positive potential as a result of its coupling to its emitter 26 by way of resistor 45. In view of the fact that only low currents prevail with this particular application of the switching means 10, noise eifects resulting from the switching processes are held to a minimum.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of ignition circuits for internal combustion engines differing from the types described above.

While the invention has been illustrated and described as embodied in ignition circuits for internal combustion engines including electronic and magnetic means, it is not intended to be limited to the details shown, since various modifications and structural changes may be made with out departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An ignition arrangement for an internal combustion engine, comprising, in combination, a plurality of spark plugs to be ignited simultaneously at the same instant of time; a plurality of ignition coils having primary and secondary windings for firing said spark plugs, each of said ignition coils being associated with one of said spark plugs; a plurality of electronic switching means connected in series with said primary windings of said ignition coils, each of said electronic switching means being associated with one of said primary windings only and being independent of the other of said switching means, and each of said secondary windings being connected to one of said spark plugs; a single DC power supply connected to said electronic switching means; and control circuit means operating as a function of the speed of said engine and actuating said electronic switching means, whereby said plurality of electronic switching means are switched sim ultaneously to their non-conducting states and produce ignition of said spark plugs at the same instant of time.

2. The ignition arrangement as defined in claim 1 including decoupling resistor means connected between said electronic switching means and said circuit control means.

3. The ignition arrangement as defined in claim 1, including a decoupling diode means connected between said electronic switching means and said circuit control means.

4. The ignition arrangement as defined in claim 3, including resistor means connected in series and between said decoupling diode means and said circuit control means.

5. The ignition arrangement as defined in claim 1, wherein said circuit control means comprises interrupting switching means; and cam means driven by said engine and actuating said interrupting switching means, whereby the rotation of said cam actuates periodically said interrupting switching means as a function of the speed of said engine.

6. The ignition arrangement as defined in claim 1, wherein said circuit control means comprises transistor means having three terminals, two of said terminals being connected in series with said DC power supply and said electronic switching means; and mechanical switching means mechanically coupled and actuated by the crank shaft of said engine, the third one of said terminals of said transistor being connected to said mechanical switching means, whereby said mechanical switching means is actuated periodically as a function of the speed of said engine.

7. The ignition arrangement as defined in claim 6, wherein said mechanical switching means is a cam operated switch for periodically connecting and disconnecting a control voltage to said third terminal of said transistor.

8. The ignition arrangement as defined in claim 6, wherein said mechanical switching means is a pulse generat'or providing induced pulses as a function of the speed of said engine.

9. The ignition arrangement as defined in claim 8, in cluding monostable multivibrator means connected to said pulse generator means and to said transistor means for applying pulses periodically to said transistor means as a function of the speed of said engine.

10. The ignition arrangement as defined in claim 1, including a control transistor in one of said electronic switching means, the emitter-collector path of said control transistor being connected in series with said primary winding of said ignition coil and the base of said control transistor being connected to said circuit control means.

11. The ignition arrangement as defined in claim 10, including connecting means for connecting the collector of said transistor to one end of said primary winding of said ignition coil, the other end of said primary winding being connected to the negative polarity terminal of said DC power supply, the emitter of said transistor being connected to the positive terminal of said DC power supply; andlimiting resistor means connected between the base of said transistor and the negative polarity terminal of said DC power supply.

References Cited UNITED STATES PATENTS 1,428,635 9/1922 Hunt 123-148 1,458,375 6/1923 Aiken 123-148 2,328,444 8/1943 Francis 123-148 3,020,897 2/1962 Sekine et al.

3,167,705 1/1965 Sohner.

3,171,046 2/ 1965 Meland.

3,202,146 8/1965 Short et al.

LAURENCE M. GOODRIDGE, Primary Examiner. 

